This is a revised application which addresses issues raised in the IRG Summary Statement of 04/12/94. It concerns a three-year, case/control investigation of the role of drug use and abuse in homelessness among 400 indigent men and women in New York City with no history of major mental illness. Inspired by a recently completed investigation of risk factors for homelessness among the severely mentally ill in which the same study design was employed, the proposed study will test hypotheses on differences between the homeless and never homeless in three domains: individual functioning, family background, and prior service use. The 200 homeless cases, stratified by gender, will be recruited from among the newly homeless seeking care in a municipal shelter. The 200 never homeless controls, stratified by gender and matched with cases on age and ethnicity, will be selected from among applicants for public assistance. Structured assessments will be used to investigate patterns of drug and alcohol use and abuse, social functioning and psychiatric status, childhood antecedents and family characteristics; and prior use of substance abuse, health, and social welfare services. Although concurrent drug and alcohol abuse have been found to be important risk factors for homelessness among the severely mentally ill, information has been lacking on samples of indigent adults with no current or past psychotic disorder and no history of psychiatric hospitalization. Thr proposed study will identify the role of drug use and abuse as risk factors for homelessness in this population, and clarify the importance of drug use and abuse in relation to other possible risk factors associated with individual and family functioning. Deinstitutionalization of mental health services has been implicated in the etiology of homelessness among the severely mentally ill, but there has been little data to determine if gaps in community health, mental health, and substance abuse treatment programming inadvertently contribute to the problem of homelessness among indigent adults with no major mental illness. Comprehensive assessment of risk factors for homelessness provided by the proposed study may suggest new strategies for prevention and early intervention.